The current obesity epidemic warrants improved strategies for preventing and treating this increasingly devastating disease. Recently, our collaborative group examined the obesity-prone Samoan population and identified a missense variant in a putative transcriptional regulator (CREBRFR457Q) that increases BMI and adiposity. Little is understood about CREBRF and even less for the mechanisms by which its obesity-risk variant influence these phenotypes in humans. Because food intake, energy expenditure, and fat storage are orchestrated between the periphery and the brain, we examined in murine models that CREBRF was expressed and enriched in the hypothalamus throughout embryonic development and in adulthood is regulated during feeding state in a cell-specific manner. Therefore, the overall objective of this proposal is to understand how CREBRF and its obesity-risk variant contribute to the central regulation of energy homeostasis and, more specifically, to the development and function of POMC and AgRP neurons in the arcuate nucleus of the hypothalamus during nutritional stress in a sex-specific manner. Our central hypothesis is that CREBRF and its obesity-risk variant influence proliferation, differentiation, and subsequent activation/output of key hypothalamic neurons that control food intake, energy expenditure, and body weight. This hypothesis is supported by the following preliminary data: 1) humans expressing the CREBRFR457Q variant have increased BMI and adiposity, 2) mice lacking CREBRF have reduced body weight and food intake, 3) wild type CREBRF is reciprocally regulated in POMC and AgRP neurons in response to fasting, and 4) CREBRF is expressed in the embryonic hypothalamus and induced corresponding with neurogenesis. The central hypothesis will be tested using available cell and mouse models to achieve the following two specific aims: 1) to determine the impact of CREBRF and its obesity-risk variant on embryonic hypothalamic development, and 2) to determine the impact of CREBRF and its obesity-risk variant on gene expression in key adult hypothalamic neurons that regulate energy balance during various feeding states. This research is innovative because it uses a multidisciplinary approach and state-of-the-art techniques to elucidate mechanisms by which a novel human obesity-risk variant in a poorly understood gene influences the central regulation of energy homeostasis. This research is significant because it is directly relevant to populations with a high prevalence of the risk allele and because it is likely to reveal novel insights into the general regulation of energy homeostasis and pathogenesis of more common obesity in humans. These findings are expected to have broad translational impact because they will provide fundamental understanding for a relatively unknown gene and reveal novel mechanisms that can be targeted for prevention and/or treatment of obesity in a sex-specific manner. Additionally, this NIDDK R21 will support the generation of high-impact publications and preliminary data for subsequent R01 proposals further examining the role of CREBRF on hypothalamic development, in energy homeostasis, and other disease-relevant processes.